Officials have taken a suspect into custody just 24 hours after first reports that a ricin-laced letter had been intercepted at the offsite Senate mail-handling facility.

According to reports by NBC News and other outlets, the investigation by U.S. Capitol Police and the Federal Bureau of Investigation culminated in the arrest of Paul Kevin Curtis in Corinth, Miss.

The letter, addressed to Mississippi Republican Sen. Roger Wicker was reportedly signed by “KC.”

A similar-looking envelope was caught at a mail screening center earlier on Wednesday, bound for President Barack Obama.

“There has been an arrest as a result of great work by the USCP in developing the information on the suspect and tracking him, forensic work by several partners and dogged street work by the FBI,” Senate Sergeant-at-Arms Terrance W. Gainer said in a statement to CQ Roll Call. Gainer wouldn’t comment on the suspect’s name or place of arrest. “The investigative follow-up is significant and ongoing,” he added.

The arrest could help put nerves at ease on Capitol Hill, where lawmakers, staffers and tourists have been on heightened alert the past three days, particularly in the wake of Monday’s bombings at the Boston Marathon.

The Capitol Police shut down portions of the Hart and Russell Senate office buildings on Wednesday morning to respond to suspicious hand-delivered packages, both of which tested negative for hazardous materials.

Sens. Carl Levin, D-Mich., and Jeff Flake, R-Ariz., also reported suspicious letters in their respective state offices that were both being tested for ricin or other substances.